Positioning fixture



Jne 12, 1945. F. L RATMCZAK 2,3??,95

POSITIONING FIXTURE Origial Filed Dec. ll, 1942 4 `Sheets-Sheet l 7W INVENToR. www@ June 12, 1945.

F. l. RATAlczAK i 2,377,965

POSITIONING FIXTURE original Filed Dec, 11, 1942 4 sheets-sheet 2 J INVENTOR.

June 12, 194% F. l. RATAICZAK PosITIoNING FIXTUR Original Filed Dec. l1,

1942 4 Sheets-Sheet 3 INVENTOR.

June 12,'1945.

POS ITIONING FIXTURE Original Filed Dec. l1, 1942 4 Sheets-Sheet 4 o@ y v /70 @y I sa J -dld//INVENTOR.

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F. l. RATAiczAK 2,377,965

" In the drawings:

Patented June 12, 1945 PosiTIoNING IXTURE "Francisl, Rataiczak, Dayton, Ohio, assigner to `General Motors Corporation, Dayton, Ohio, a

corporation of Delaware Original application December 11, 1942, Serial No.-`` 468,615, which is adivision of application Serial No. 395,645', May 28, 1941. application September Divided and this 9, 1943, Serial No.

i 7 claims. (oies- 181) This invention relates to. refrigerating apparatus and-more particularly to a positioning fixture for `use `1n fabricating a motor-compressor unit.

' This application is a division of my copending application Serial Numbe1"468,615,led Decem- I berll, 1942,A which inturn is a division of my copending application Serial Number 395,645, filed May 28, 1941.

One of theiobjects of this invention is to provide a positioning xture for facilitating-mass production ofmotor-compressor units.

Another object of this invention is to provide means for detecting errors in alignmentin motorcompressor parts during the assembly'of these partsV A further object of this invention is to simplify the assembly of4 the motor-stator' within Athe motor-compressorhousing.

`Further objects and advantages of the present invention will be apparent from the following description, reference being had to* the accompanying drawings, wherein a preferred form of the present invention is clearly shown. i

Fig. 1 isiapartly diagrammatic view unit in section; i

Fig. 2 is a sectional View of the compressor unit taken on the line 2--2 of Fig.` 1; f

Fig. 3 is a plan View of the motor-compressor9 unit `with the cover oflthe casing removed and with the motor-rotor broken away;

Fig. 4 shows the comtruction of the main shaft and themotor-rotor;

Fig. 5 is an enlarged sectional Viewshowing the suction valve assembly;

Fig. 6 is an elevational view of the main casing `without, the heat radiating uns and withv a `portion of the casing broken away so as 'to more clearly show the" motor-stator mounting' means; f1

Fig. 7 is a plan View of the main easing and the motor-stator and illustrates the manner in which the main lcompressor `casing is inserted through the motor-stator;

Fig. 8 is `an `elevational View partly in section showing thel apparatus used for aligning the main `compressor cylinder with the motor-stator; Yand of Aa reirigerating system showing the motor-compressor of various elements. In the ordinary motor-com- `65 pressor design the accumulation of tolerances materially affects the efficiency of they unit and frequently renders the unit completely inoperative, in which case, it becomes necessary to reoperate some of the parts or to `match certain parts with other parts in which the dimensional errors balance out upon assembly. This is especially true in case the compressor and its associated motor-rotor is assembled with a stator whichfis not perfectly concentric with the main bearing due to tolerances necessary in the manufacture of the statoror due to a slight error-in the manufacture of the stator mounting means or due to an accumulation of errors in the motorstator and its mounting means.

Referring now to Fig. 1 of the drawings, in which I have shown a preferred embodiment of my invention, reference numeral lll designates generally a hermetically sealed motor-compressor unit. Reference numeral I2 designates a substantially cup-shaped stamped sheet metal casing which'forms the main support for theA compressor assembly I4 and also the motor-stator'l. Reference numeral I8 designates a conventional motorrotor. A stamped sheet metal end cap Il closes the upper end of the'cup-shaped casing element 4 l2 and forms therewith a high. pressure refrigerant vapor chamber. The end cap Ilr is welded or otherwise secured to` the main casing l2. Heat conducting fins 2l may be secured to the outside of the casing element I2 to help dissipate the heat.

As best sho-wn in Fig. 5, the upper side of the adapter block 32 is provided with a recess 36 in which a check valve, generally designated by the reference numeral 38 is mounted. The valve 3l) is heldin place by the compressor end plate element which rests upon the adapter block 32 and one or more mounting blocks 39 which are welded or otherwise secured to the bottom wall of the casing I 2. The upper surfaces of the blocks 32 and 39 are machined so as to be perpendicular to the motor-stator support surfaces described hereinafter.

As best shown in Fig. 1, the compressor assembly I4 comprises a lower end plate 50, a cylinder element52 and an upper end plate 54 which has formed integrally therewith the main bearing 55. The upper end plate 54, as shown in Fig. 3, carries a conventional discharge valve assembly 58 which controls the flow of refrigerant through the compressor outlet 60 provided in the endplate `'54. An impeller (i2 is provided within the cylinder 52. The impeller (52 is mounted on the eccentric 64 which -causes the impeller to A divider block 66 cooperates with the cylinder 52 and the impeller 52 in accordance with wellknown practice. A spring 68 biases the divider block into engagement with the impeller 62. The outer end of the spring rests against the spring retainer 10.v The spring retainer is slipped into place before the cylinder 52 is clamped between the end plates 50 and 54 and is held in place by the end plates 50 and 54.

The end plate 50 is provided with a tapered passage 18 which conveys the low pressure refrigerant vapor from the inlet valve 38 to the compression chamber 80. By virtue of the taper in the walls of the passage 18, any slight misalignment between the end plate 50 and the inlet valve I 38 will not interfere with the free iiow of refrigerant from the inlet valve to the compression chamber.

The motor-stator I6 is held in place by means of special clamps such as |02. The clamps |02 are initially formed as shown in Fig. 6, and are spot welded or otherwise secured to the shell I2. In the prior art devices, it is customary to provide a press fit between the outer shell of the compressor and the motor-stator. In such an arrangement, it is very difficult to properly hold the motor-stator in place unless a very heavy cast iron frame or the equivalent is used; and once the motor-stator is in place, it is very dilcult to remove it for inspection or repair purposes. By virtue of the clamping arrangement shown, a light weight sheet metal casing may be used and the nal sizing operation may be performed merely by forcing a die of proper size into the opened end of the casing so as to deform the projecting portion |04 of each clamp |02 the necessary amount. This arrangement of parts and method of sizing eliminates the necessity for turning the inner surface of the outer shell I2 to size on a lathe. Furthermore, the clamping elementsv |02 serve to compensate for any taper or irregularity in the walls of the shell |2. It is difficult to form the outer sheet metal casings to any exact dimension since the strains and stresses in the sheet metal casing produced by the drawing operation tend to distort the walls of the casing. The clamps |02, however, sufficiently compensate for such distortions.

After the motor-stator has been inserted in place, the projecting ends |06 of the clamp elements |02 are bent over onto the upper side of the motor-stator so as to hold the motor-stator in a fixed position. This not only reduces the cost of construction and facilitates the assembly of the apparatus, but also facilitates the removal of the motor-stator in the event that it becomes necessary to replace the motor-stator. The lower ends of the clamps |02 are provided with ears |01 which limit the downward movementl of the motor-stator.

In order to avoid the harmful accumulation of tolerances in dimensions in assembling the various parts, the various parts of the unit are assembled in the following manner. In assembling the various elements that go to make upl the compressor unit, the rst step is to position the cylinder 52 with respect to the lower end wall 50. This is done by means of a conventional positioning mandrel (not shown) which holds the member 52 in proper alignment with the member 50 while one or more bolts such as bolt |50 (see Fig. 3) is or are tightened so as to clamp the elements 50 and 52 together in their proper the impeller B2.

relationship. After the elements 50 and 52 have been fastened together in proper alignment, the impeller 62, the divider block 66, the divider block spring 68 and the spring retainer 10 are inserted in place and the upper end plate 54 is bolted to the cylinder 52 and the lower -end plate 50 by means of bolts 51. A positioning mandrel (not shown) is used for holding the end plate 54 in alignment while the bolts 51 are being tightened.

The compressor assembly may then be inserted downwardly through the opening in the motorstator as shown in Fig. 7. The compressor assembly is of such shape and size that it may readily pass through the opening in the motorstator. After the compressor assembly has been slipped into place in the bottom of the casing |2, a specially constructed positioning fixture |52 is used for aligning the main compressor bearing with the inner surface of the motor-stator.

The positioning fixture |52 comprises a central shaftl |54 provided with a knurled handle |56. The main portion of the central shaft |54 has a diameter corresponding to the internal -diameter of the main compressor bearing 55. Another portion |58 of the central shaft |54 has a diameter slightly less than the internal diameter of The lowermost portion |60 of the central shaft |54 has a diameter corresponding to the internal diameter of the bearing 25 provided in the lower end plate 50 for the lowermost portion 23 4of the main compressor shaft I9. The positioning fixture |52 has an intermediate sleeve member |62 which is slidably mounted on the central shaft |54. The intermediate sleeve |62 is provided with a knurled handle portion |64. The lower end of the sleeve |62 is tapered for a purpose explained hereinafter. The main body |66 of the positioning fixture |52 has a central aperture through which the sleeve |62 and the shaft |54 may be inserted. The outer diameter of the main portion of the element |66 is slightly less than the internal diameter of the motor-stator I6.

As best shown in Fig. 9, the main body |66 of the positioning fixture is provided with four 1ongitudinally extending slots |68 in each of which is mounted a shoe element |10. Each shoe element |10 is provided with a shank |12 which passes through a radially extending hole |14 formed in the body |66. The inner end of each shank is provided with a cam surface |16 which is adapted to engage the tapered portion of the sleeve |62. The element |66 is provided with a shoulder |18 which limits the movement of the element |66 within the motor-stator I6. The arrangement is such that when the positioning xture is inserted into the motor-stator and the sleeve element |62 is moved into the position in which it is shown in Fig. 8, the sleeve |62 cams the shoes |10 into engagement with the motorstator, whereby the central shaft |54 of the positioning mandrel may be used for lining up the compressor assembly with respect to the motorstator.

The main body |66 of the positioning fixture is provided with a plurality of apertures through which access may be had to the cap screws 56 which secure the compressor assembly to the mounting blocks 32 and 3S. While the positioning fixture is in place, the cap screws 56 are securely tightened so as to rigidly hold the compressor assembly in position. After having tightened the cap screws 56, the positioning mandrel is removed. By-removing the sleeve |64, the shoes |10 release their hold on the walls of the rotor I8 and its associated shaft- I9 may be dropped into place.

Inasmuch as the above described construction allows the motor-rotor to be secured to the shaft I9 prior to the assembly of the shaft in the main bearing, it is possible to true-up the outer diam-v eter of the motor-rotor after it has been mounted on the shaft, thus eliminating the accumulation of tolerances in the concentricity of the main shaft, the internal bore of the motor-rotor and the external diameter of the motor-rotor.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the clairns which follow.

What is claimed is as follows:

1. A positioning fixture for positioning a compressor bearing assembly in' concentric relationship Ito a motor-stator comprising, in combination, a central shaft element for engaging said compressor bearing assembly, an inner sleeve member slidably mounted on said central shaft,

an outer sleeve member slidably mounted on said inner sleeve member, the outer diameter ofsaid outer sleeve member being slightly less than the inner diameter of said motor-stator, a plurality of stator engaging shoes carried by said outer sleeve member, and means carried by said inner sleeve member for forcing said shoes into engagement With the inner wall of said motor-stator so as to centrally locate the central shaft with respect to said motor-stator.

2. A positioning fixture for positioning a compressor bearing assembly in concentric relationship to a motor-stator comprising, `in combination, a central shaft element for engaging said compressor bearing assembly, an inner sleeve member slidably mounted on said central shaft, an outer sleeve member slidably mounted on said inner sleeve member, the outer diameter of said outer sleeve member being slightly less than the inner diameter of said motor-stator, a plurality of stator engaging shoes carriedby said outer 3. A positioning fixture for positioning a bearing in concentric relationship to a housing having a cylindrical opening comprising, in combination, a central shaft element for engaging said bearing, an inner sleeve member slidably mounted on said central shaft, an outer sleeve member slidably mounted on said inner sleeve member, the outer diameter of said outer sleeve member being slightly less than the inner diameter of said opening, a plurality of shoes carried by said outer sleeve member for engaging the Wall of said opening, and means carried by said inner sleeve member for forcing said shoes into engagement with the Wall of said opening so as to centrally locate the central shaft with respect to said housing.

4. A positioning fixture for positioning a bearing in the lowerpart of a cup-shaped casing substantially in concentric relationship to the central axis of said casing comprising in combination, a shaft element for locating said bearing within the lower part of said casing, a sleeve member slidably mounted on s-aid shaft, an outer sleeve member slidably mounted on said first named sleeve member, the outer diameter of said Iouter sleeve member being slightly less than the inner diameter of said casing, a plurality of shoes carried by said outer sleeve member for engaging the inner Wall of said casing, and means for forcing said shoes into engagement with the inner wall of said casing so as to' centrally locate said shaft with respect to the inner Wall of said casing.

5. Apositioning fixture for positioning an element within a recess in a support comprising in combination, means slidable into said recess and having one portion adapted to engage said element to hold said element in place and having another portion adapted to engage the walls of said recess,` and an aperture in said means through which a tool may be inserted down into said recess to fix said element Within said recess.

6. 'A positioning fixture for positioning a compressor bearing assembly in concentric relationship to a motor-stator comprising in combination, a mandrel, a tapering member mounted thereon, expanding members carried l by said mandrel and operated by said tapering member for engaging the inner surface of said motorstator, and means carried by said mandrel for positioning said bearing assembly in concentric relationship to said motor-stator.

7. A positioning fixture for positioning a compressor bearing assembly in concentric relationship to a motor-stator comprising in combination, means having one portion adapted to engage said compressor bearing to hold said bearing in place and having another portion adapted to engage the Walls of the central opening of said motor-stator, said means having aperture means therein through which a tool may be inserted through said central opening to fix said bearing assembly in place.

FRANCIS I. RATAICZAK. 

